High frequency tube coaxial transmission line



March 14, 1967 J. K. MANN 3,309,631

HIGH FREQUENCY TUBE COAXIAL TRANSMISSION LINE Original Filed Dec. 16, 1959 U3 INVENTOR Joseph K. Mann Lg A Homey Flee 9, Ser. No. 859,964, new t Oct. 9, i962. Divided this June 18, 1962, Ser. No. 293,374

1 Clain {'Cl. 33333) This application is a divisional application f co-p United otates patent application, Scr. No. 859,954, fied Dec. 16, 1959, for improvements in high frequency tube apparatus, now US. Patent No. 3,958, Q6 issued Oct. 9, 1962.

The present invention relates in general to high frequency tube apparatus, and, more specifically, to a novel high frequency, high power velocity modulation tube which is extremely useful for providing a continuous wave output high average powers and which is easily tunable over a wide frequency range. Such tubes are especially useful as output tubes in tropospheric forward scatter communication link, and for transmitting tubes covering the UHF-TV band.

Heretofore multicavity li ystron amplifiers have been built which would provide relatively high output powers on the order of one kw. average at S frequency hand. These tubes suffered from short life and complexity.

The present invention provides a compact, rugged permanent magnet, air cooled, high power, multicavity klys tron amplifier capable of delivering average output powers in the order of one or more lrw. and at the same time have the greatly enhanced tuning range of approximately 40 percent and a gain of 50 db. The wide tuning range is obtained by the use of an improved tuning apparatus first disclosed in the co-pending application, Ser. No. 749,225, now US. Patent No. 2,994,009, invented by Robert C. Schmidt et al. and wherein both the inductive and the capacitive parameters are varied in a desired manner to tune the cavity.

A feature of the present invention is the provision of a novel coaxial output Window and coupling means providing both the vacuum seal and a frequency sensitive impedance transformer for obtaining optimum coupling over a wide band of frequencies.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein,

PEG. 1 is a partly cut away side elevational view of a novel high power klystron amplifier of the present invention,

FIG. 2 is an enlarged detailed view of a portion of the structure of FIG. 1 delineated by line 2-2.

Referring now to the drawings, there is shown in FIG. 1 the external, partially cut away configuration of the novel tube apparatus of the present invention. More specifically, a segmented tubular cathode assembly 11 provides a source of electrons which are formed into a pencil-like beam and projected longitudinally of the tube apparatus. A plurality of substantially rectangular cavity resonators, including an input cavity 12, second and third cavi.les l3 and i4, and an output cavity are centrally apertured to allow the passage of the pencil-like beam of electrons therethrough.

The individual cavity resonators 1245 are tunable over a wide range via a plurality of novel tuner assemblies 16 which will be more fully described below. The beam, after passing through the output cavity resonator i5, is collected in a collector assembly 17. The thermal energy generated by the impinging electrons within the collector assembly 17 is carried away by an air stream circulated about the collector assembly 17.

RF. signal energy, which it is desired to amplify, is fed to the input cavity 12 by a vacuum sealed coaxial connector 13. The signal energy velocity modulates the beam as it passes through the input cavity 1.2. Velocity modulation of the beam is transformed into current density modulation in drift spaces between the input cavity 12 and the first buncher cavity 13. The buncher cavities 13 and 14 further velocity modulate the beam to produce greater current density modulation of the beam at the output cavity 15. The output cavity extracts RF. energy from the current density modulated beam.

The output R.F. energy is coupled outwardly of the output resonator 15 via a vacuum sealed RF. coaxial line 19 described in detail below and is fed to a suitable load, not shown, such as, for example, an antenna. A permanent magnet comprising two shell-shaped magnet sections 21 bolted together by bolts 21a and clamped onto a pole piece at each end of the tube apparatus, containing the cavity resonators, surrounds the central part of the tube apparatus on two sides and provides a strong axial'magnetic field longitudinally of the tube for confining the pencil-like beam of electrons. Each of the magnet sections 21 is provided with a handle 21b for lifting the tube assembly with the magnet attached thereto.

An output coupling loop is formed by a strap 52 as of copper vacuum sealing the end of the hollow center conductor 53 of the output coaxial line 19 and connecting this center conductor 53 to the outer conductor 5 3-. Near its external end the outer surface of the outer conductor 54 is provided with a shoulder which engages a cooperating shoulder on a hollow cylindrical member 55 as of copper which surrounds the outer conductor and is vacuum sealed within an output port St: in the output cavity 15. The external ends of the outer conductor 54 and the cylindrical member 55 are vacuum sealed together as by brazing.

An annular wave permeable Window member 57' of ceramic as, for example, alumina is coaxially disposed with respect to the inner and outer conductors 53 and 5d and vacuum sealing the space therebetween as by brazing. The thickness and position of the window 57 are selected to present a predetermined discontinuity in the transmission line and the desired discontinuity can easily be achieved by the use of alumina ceramic which has low loss and a higher dielectric constant on the order of 9 as compared with a dielectric constant of about 3 to 6 for glass previously used for wave permeable windows.

Thus, the ceramic window 57 serves to form the vacuum seal for the RF. output as well as a frequency sensitive impedance transformer which transforms the load impedance to the optimum impedance for the tube at all frequencies of operation.

This novel window requires no adjustment over the range of the tube, as frequently required in the past, or the necessity for a matched window as previously used in combination with a loading member.

A hollow cylindrical output coupling flange 59 for bolting the coaxial line 19 to a standard 1%" coaxial line 553 by means of a bullet type adaptor assembly 5% surrounds the cylindrical member 55 and is fixedly secured thereto by Cap screws on a split ring member which fits within an annular recess in the outside surface of the cylindrical member 55. An outer conductor extension 62 slidably fits within the external end of the outer conductor 54, seats against a shoulder on the inside surface of the outer conductor 55 and bears against the outer conductor of the coaxial line 59. In this manner nothing bears against the vacuum sealed joint between the outer conductor 54 and the cylindrical member 55 so that the force of shocking blows is not directed against this seal.

The collector assembly 17 serves to collect the electron beam after it passes through the output cavity 15. In the collector assembly 17, a collector pole piece 63 as of steel is secured to the end wall of the output cavity 15 in a vacuum tight manner by means of annular flanges 63a secured together by means of a heliarc Weld. A hollow cylindrical collector 64 as of steel is secured at one end thereof to the pole piece 63 and near the other end to a circular plug member 65 as of copper provided with a circular groove on either side thereof, these grooves being radially spaced from one another to allow for differential expansion between the collector 64 and the plug member 65. A circular plate 66 as of steel covers the end of the collector 64. The steel collector minimizes the magnetic field Within the collector to prevent focusing of secondary electrons back into the resonator section of the tube apparatus. A plurality of radially extending fins 64a fixedly secured to the collector 64 substantially over the length thereof provide means for dissipating the collector heat by means of an air stream.

Since many changes can be made in the above construction and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

A high frequency coaxial transmission line apparatus for coupling wave energy between resonant cavity means of a high frequency electron discharge device and load means comprising; coaxially disposed inner and outer conductors; a strap member connecting said inner and outer conductors and vacuum sealing the end of said inner conductor, thereby forming an inductive coupling loop, and an annular ceramic Wave permeable window member coaxially disposed with respect to said inner and outer conductors and forming an electromagnetic wave permeable vacuum seal between said inner and outer conductors, said window member having a net predetermined lumped capacitance value in the transmission line and spaced from said strap member such that the combination forms an impedance transformer over a range of frequencies for transforming the load means impedance to the optimum impedance for the device over a range of frequencies.

References Cited by the Examiner UNITED STATES PATENTS 2,474,137 6/1949 Young 333-33 2,530,171 11/1950 Okress 333-33 2,871,397 1/1959 Priest et a1. 3155.46 2,875,369 2/1959 Chambers 3155.46 2,938,182 5/1960 Dench 33333 2,994,009 7/1961 Schmidt et al 3155.48 3,030,594 4/1962 Stitch et al 33383 3,032,726 5/1962 Fink 333-98 3,036,281 5/1962 Hilliard 333-83 3,039,068 6/1962 Greco 33398 ELI LIEBERMAN, Primary Examiner.

GEORGE WESTBY, HERMAN KARL SAALBACH,

Examiners.

S. CHATMON, C. O. GARDNER, Assistant Examiners. 

